On Runway Foreign Object Ingestion With a Variable Pitch Fan in Reverse Thrust Mode

The characterization and quantification of runway foreign object ingestion (FOI) at the end of the landing run with a variable pitch fan (VPF) in reverse thrust mode are described in this work. This is achieved by developing a novel, fully coupled computational fluid dynamics—discrete phase model (CFD-DPM) methodology that allows the tracking of individual debris, which is placed on the runway. The flow field solutions are computed by the three-dimensional (3D) Reynolds-averaged Navier–Stokes (RANS) equations, and the particulate phase is tracked in a Lagrangian way. A modern 300-seater aircraft is considered to feature a high bypass ratio geared turbofan engine architecture on a conventional twin-engine airframe in landing configuration that rolls on the runway at low speeds and a typical high engine power mode. The aerodynamic reverse thrust flow field at such low aircraft speeds is characterized by the development of a “horseshoe” vortex formed in front of the engine that significantly affects the debris trajectories. Based on this, two FOI mechanisms are identified and discussed in detail in the paper. The effect of key debris properties on FOI percentage, such as size, material density, and shape, are investigated and reported. Nonlinear, nonintuitive trends are obtained due to the two-way interaction of flow features and particles. Moreover, a nondimensional analysis that accounts for the changes in debris variables of interest is presented and provides general trends for aircraft with a VPF as the main thrust reversal unit. Generally, debris ingestion increases with lower aircraft speed and debris material density. The benefits of having a VPF are highlighted since it acts as an additional “protective layer” to the engine core and stops and redirects incoming debris from the nominal intake. The assessment of ingestion of foreign objects in realistic end-of-landing-run conditions as described in this study is important to examine the feasibility of reverse thrust-capable VPF engines for future sustainable aircraft.

A novel hysteresis phenomenon during the transition to and back from the reverse thrust mode in a Variable Pitch Fan (VPF) is identified and characterised in this work. This is done by using a three-dimensional (3D) fully transient Unsteady Reynolds averaged Navier?Stokes (URANS) with the transitioning fan blade aerofoils simulated by an adaptation of the mesh displacement method. The VPF is modelled to be transitioning in a modern 40000 lbf geared high bypass ratio turbofan engine architecture at "Approach Idle" engine power setting in a typical twin-engine airframe with the flaps, slats, and spoilers set for an aircraft touchdown airspeed of 140 knots. The transition to reverse thrust mode involves flow starvation into the engine, formation of recirculation zones in the bypass duct and the establishment of the reverse stream, all of which occurs in the opposing presence of the free stream flow at aircraft touchdown velocity. The transition back to forward flow mode involves the gradual re-establishment of the free stream which is opposed by the presence of the reverse stream within the engine. It is quantified that in the transition to reverse thrust, the blockage develops with a larger time delay than the disappearance of the blockage during the transition back due to the interplay of the temporal dynamics of fan blade motion and flow field response. The hysteresis phenomena described in this work are critical in properly developing control schedules to adapt for potential bi-stable flow field development during the landing run.

Variable pitch low pressure ratio fans could enable higher propulsive efficiency and eliminate the need for heavy thrust reversers. In this paper, the effects of the fan rotor design on reverse thrust capability have been explored by varying key parameters of NASA’s Advanced Ducted Propulsor (ADP) while maintaining cruise point performance. Reverse thrust performance has been assessed using RANS single passage CFD of the variable pitch fan system with an extended domain. This computational approach has been validated using NASA Stage 51B, an experimental variable pitch fan test case. Predicted total pressure and total pressure ratios for this case were found to agree with test data within experimental error, except where large tip region separations occurred at high incidence. Applying individual variations to rotor pitch-to-chord, radial loading distribution, and chordwise camber distribution generated changes to rotor incidence, blockage, and peak surface Mach numbers in reverse operation. An increase in gross reverse thrust of up to 8% was achieved through reductions in rotor pitch-to-chord due to improved loading and lower shock Mach numbers. Controlling section camber distributions was used to move the rotor shock downstream and was found to increase reverse thrust by up to 3%. Increasing rotor loading at the mid span relative to the tip resulted in high tip incidence and a 50% reduction in gross reverse thrust across all rotor speeds. This suggests that tip loaded designs are required for high levels of reverse thrust.

After the successful introduction of commercial turbofan engines with medium bypass ratios, NASA’s Lewis Research Center spearheaded an aircraft propulsion development program in the early 1970’s called “Quiet Clean Short-Haul Experimental Engine” commonly referred to as QCSEE. In addition to the goal of doubling the bypass ratio relative to early production turbofan engines, QCSEE led in pioneering (a) reversible-pitch composite fan blades, (b) a high bypass ratio geared fan/turbine, (c) extensive use of composites, (d) noise reduction technologies, and (e) digital electronic controls. This paper reports on the design, fabrication and testing of two propulsion systems for QCSEE by GE Aviation under contract from NASA in the mid-1970’s. The first design was an Under-the-Wing (UTW) engine, which incorporated a reduction gearbox to drive the low-speed fan with variable pitch to further improve fan efficiency along with elimination of the thrust reverser. The variable pitch fan was used for modulating forward as well as reverse thrust. This design utilized a low-pressure ratio fan (lower tip speed) at take-off and a bypass ratio of 12. The other design entitled as the Over-the-Wing (OTW) engine also used a reduction gearbox to drive a low-speed fixed pitch fan. The OTW engine configuration had a slightly higher fan pressure ratio (higher tip speed) at take-off and a bypass ratio of 10. The design and testing of these fans for the QCSEE program are presented. Key design features of the composite fan blade and the variable pitch mechanism are presented. The QCSEE design was based on a lightweight, high-speed, power turbine driving a slower speed, quiet fan that required a compatible, compact, lightweight, high-power-capability, main reduction gear. Performance results of two reduction gears designed, fabricated, and rig-tested are summarized. A summary of the development of the composite frame and nacelle is presented. Limited highlights of the digital engine control are shown. Finally, overall engine aerodynamic, acoustic, and mechanical test performance are reported in this article. The impact of each of these key QCSEE technologies to existing GE/CFM products, and their contribution to CFM’s current RISE Open Fan technology program will be discussed.

ROLE OF DEBULKING FOR BENIGN ENDOBRONCHIAL LESIONS: A CASE OF CHRONICALLY ASPIRATED FOREIGN BODY PRESENTING AS NECROTIZING PNEUMONIA

Flow channel contractions and expansions often lead to flow separation and accelerated fouling deposition, particularly around the tube support plate (TSP) in steam generators. This study employed large eddy simulation (LES) coupled with the discrete phase model (DPM) to analyze deposition mechanisms at various locations within these flow configurations. Simulation results were compared with Reynolds-averaged Navier–Stokes (RANS) models, with LES showing superior predictive accuracy, especially when sub-grid-scale turbulence effects were considered. A comprehensive analysis of near-wall flow behavior, particle trajectories, and deposition characteristics was conducted. Results indicate that fouling deposition at the TSP inlet is particularly severe, with a high risk of blockage. A deposition model specific to the TSP inlet was developed, showing that dimensionless deposition velocity initially increases and then decreases with increasing dimensionless relaxation time. For τp*<0.04, Vd+ increases proportionally to (τp*)1.18. In contrast, for 0.04≤τp*<2.1, centrifugal forces reduce deposition, following Vd+∝(τp*)−0.77. This study advances the understanding of hard fouling formation and offers strategies for mitigation in steam generators and similar systems.

This study investigates a ducted propfan in reverse mode, considering the influence of air bypass from outside the duct or air leakage after the propfan impeller. The size of the bypass windows and the dependence of the air flow rate through the bypass windows of a ducted propfan in reverse mode when changing the flight speed and the dependence of the reverse thrust of a ducted propfan in reverse mode, considering the influence of air intake from outside the duct or air leakage after the propfan impeller, are the subjects of the study. The study object is a ducted propfan with rotating blades of the impeller of a bypass ratio turbojet engine with an ultra-high bypass ratio (m = 20). The bypass windows are located behind the propfan impeller. The purpose of this study is to study the reverse thrust of a ducted propfan in reverse mode, considering the influence of air intake from outside the duct or air leakage after the propfan impeller. The flow simulation in a ducted propfan with rotating blades of the impeller of an ultra-high bypass ratio turbojet engine with an ultra-high bypass ratio was conducted under standard atmospheric conditions in the reverse mode in the range of the M number from 0.1 to 0.25 for the variants of the absence of bypass windows and with an increase in the relative area of the bypass windows from 0 to 0.63. The dependences of the change in the air flow rate through the bypass windows of the ducted propfan when changing the speed and the reverse thrust characteristics of the ducted propfan in the reverse mode were obtained. The flow visualization in several modes is presented, which confirms the efficiency of air bypass behind the propfan impeller. The scientific novelty and practical significance of the research results lie in the fact that new data were obtained on determining the rational size of the bypass windows and the dependence of the change in air flow rate through the bypass windows of a ducted propfan in reverse mode on the change in speed and thrust characteristics of the reverse of the ducted propfan in reverse mode, considering the influence of air intake from outside the hood or air leakage after the propeller fan impeller.

BackgroundThis retrospective study investigated the incidence rate of accidental foreign body aspiration and ingestion according to patient sex, age, and dental department. This study aimed to verify whether the incidence rate is higher in geriatric than in younger patients and whether it is different among dental departments.MethodsAccidental foreign body aspiration and ingestion cases were collected from electronic health records and the safety report system of Yonsei University Dental Hospital from January 2011 to December 2017. The collected data included patients’ age, sex, medical conditions, treatment procedures, and foreign objects that were accidentally aspirated or ingested. The incidence rate was calculated as the number of accidental foreign body aspirations and ingestions relative to the total number of patient visits. Differences depending on the patients’ sex, age, and dental department were statistically identified.ResultsThere were 2 aspiration and 37 ingestion cases during the 7-year analysis period. The male to female incidence ratio was 2.8:1. The incidence rate increased with age and increased rapidly among those aged 80 years or older. Seven of the 37 patients with accidental foreign body ingestion had intellectual disability, Lou Gehrig’s disease, dystonia, or oral and maxillofacial cancer. The incidence rate was highest in the Predoctoral Student Clinic and the Department of Prosthodontics. The most frequently swallowed objects were fixed dental prostheses and dental implant components.ConclusionThe incidence rate of accidental foreign body aspiration and ingestion differed according to patient sex, age, and dental department. Dental practitioners must identify high-risk patients and apply various methods to prevent accidental foreign body aspiration and ingestion in dental clinics. Inexperienced practitioners should be particularly careful.

ASPIRATION OF NASAL RING IN YOUNG HEALTHY FEMALE ADULT

Background: Foreign bodies are frequently encountered in the field of otolaryngology, specifically within the domains of the ear, nose, and throat (ENT). Serious complications, such as tympanic perforations and bronchoaspiration, are infrequently observed. Objective: To see the common site of impactions and complications associated with Foreign Bodies in the UADT. Methods: The Department of Otolaryngorhinology and Head-Neck Surgery at Dhaka Medical College Hospital conducted a cross-sectional study inside a hospital setting. The study was conducted from March 23, 2019, to September 22, 2019. The study included individuals who had a prior medical record of either inhaling or being impacted by a foreign object, as well as individuals who had a history of difficulty swallowing. Results: In this study, the majority of patients (70.0%) were found to be within the age range of 0 to 10 years. The average age of the patients was 6.1±2.8 years. This study found that foreign bodies were frequently observed to be impacted in the nose (42%), oesophagus (20%), and throat (38.0%).There are three main categories of foreign bodies: metallic foreign bodies, which account for 36.0% of cases, non-metallic foreign bodies, which account for 44.0% of cases, and living foreign bodies, which account for 20.0% of cases. The present study has provided evidence that non-invasive treatment methods, specifically direct vision only, accounted for the majority (42.0%) of the treatment approaches utilized. Laryngoscopy was deemed necessary in 38.0% of the patients, whereas esophagoscopy was performed in 14.0% of the cases. The present investigation involved the performance of endoscopic removal of foreign bodies (FB) in 6.0% of cases. Within the scope of this inquiry, it was noted that three subjects experienced postoperative challenges, encompassing sensations of discomfort, instances of bleeding, and issues associated with anesthesia. Conclusion: The majority of instances involving foreign .....

Turboprop aircraft may face a variety of harsh flight environments during flight, and various foreign objects may be sucked into the engine, among which the inhalation of sand can lead to erosion of the blades of the compressor. Such ingestion often results in compressor blade erosion, which can lead to engine surge and power loss. Therefore, this study explores the aerodynamic and sand separation characteristics of the inlet channel with a bypass channel through numerical simulation methods. ANSYS Fluent software is used to simulate the six-bladed propeller rotation based on the slip-grid technique by combining the unsteady Reynolds-averaged Navier-Stokes equations (URANS) and shear stress transport (SST) turbulence model. A Lagrangian discrete phase model (DPM) is applied to track the motion of standard coarse sand. The focus is on analyzing the mechanism of different propeller speeds and scavenge ratio (SCR) on the separation efficiency (η).

ObjectivesTo review the cases of accidental aspiration and ingestion of foreign objects during dental procedure, and to emphasize the importance of thorough documentation of the accidents.MethodsA comprehensive search on (dental procedure/treatment/practice), (aspiration/inhalation), and (ingestion/swallow) was performed for all years before 1st October 2014 available. The statistic analysis was made on the variables including journals and reported year, patients’ age, gender, general conditions, dental procedure and location for procedure, foreign objects, site of involvement, possible causes, anesthesia during procedure and treatment, symptoms, treatment time and treatment modality, follow-up, and so on.ResultsA total of 617 cases reported by 45 articles from 37 kinds of journals were included and analyzed. Most reports made detailed record. While some important variables were recorded incompletely, including patient’s general conditions, location for procedure, clinical experience of the involving dentists, tooth position of procedure, possible causes, and anesthesia during procedure and treatment for the accident.ConclusionsAspiration and ingestion of foreign objects are rare and risky complication during dental procedure. Each accident should have thorough documentation so as to provide enough information for the treatment and prevention.

A seven-year-old girl was referred to the emergency ward at the Khatamolanbia Hospital, Zahedan, Iran, in March 2012 after she fell face-first onto a pencil she was holding. The blunt end of the pencil had entered the orbit beneath the medial canthus. Upon ophthalmological examination, the ocular globe was intact but laterally displaced and vision in the left eye had diminished to only light perception. Moreover, the examination revealed a positive relative afferent pupillary defect in the left eye. Further funduscopic examinations were not performed due to the patient's condition. Her vital signs were normal and she was conscious without any neurological deficits. Computed tomography (CT) scans of the brain without contrast revealed a foreign body in the medial left orbit which had passed through the superior orbital fissure into the cranium near the temporal lobe and was positioned laterally to the cavernous sinus [Figure The foreign body had passed next to the petrous apex, tangentially to the brainstem and had entered the cerebellum to a depth of 4 cm. A four-vessel angiography produced a normal angiogram [Figure

During a surgical procedure, each of the medical staffs would have different postures. Supporting medical staff such as anaesthesiologist would stand in upright condition with straighten-forearm, while medical staff that is performing surgical procedures is in bent-forearm posture. The positioning of forearm might interrupt the air supplies from the ceiling-mounted diffuser, that serves to remove the airborne particles from the surgical zone. Consequently, the movement of particles in the surgical zone is affected, and the tendency of particles to fall onto the patient’s wound is increased. This situation could elevate the chances of a patient contracting surgical site infections and could increase the risk of death. The present study aims to examine the effects of medical staff’s forearm posture on the number of particles falling onto the patient. A simplified computational fluid dynamics (CFD) model of the operating room was developed and validated based on the published data. An RNG k-ε turbulence model based on the Reynolds-Averaged Navier-Stokes (RANS) equations was used to simulate the airflow, while a discrete phase model was used to simulate the movement of the airborne particles. Results show that bent-forearm of medical staff obstructed the downward airflow to remove the particles released by the medical staff. Approximately 37 particles/m3 accumulated in the chest region of the medical staff. A high particle accumulation is also observed at the gap between the staff’s legs due to the stagnant airflow.

A statistical study was made of 137 cases of esophageal and 10 cases of tracheobronchial foreign bodies treated in our clinic during the 11 years from 1983 to 1993. The results were as follows:1) Of the 137 cases of esophageal foreign bodies, 68 were males and 69 were females. There were no year-to-year changes in the incidences and sex distributions.2) Two peaks were observed in the age distribution of the esophageal foreign bodies, one in infants under 9 years old and the other in adults over 50. These were especially prominent in male infants and female adults.3) The foreign objects were PTPs (press through pack for medicine, 24%), coins (21%), fish bones (17%), artificial teeth (11%) and others. The most frequent object in the infants was coins; on the other hand, PTPs, fish bones, artificial teeth and pieces of meat were frequently observed in adults.4) The present results indicate that the incidence of the elderly people over 70 and the percent of PTP foreign bodies of our clinic were higher than reported elsewhere.5) Of the 10 cases of tracheobronchial foreign bodies, 7 were males and 3 were females. The annual incidence has not changed markedly.6) Eighty percent of the total tracheobronchial foreign body cases were under 2 years old, and 20 percent were over 70 years old.7) Beans were the most common tracheobronchial foreign bodies in infants, and false teeth were found in 2 cases of elderly people. Foreign bodies were more often seen in the right bronchus.8) In order to prevent esophageal and tracheobronchial foreign bodies, it is necessary to emphasize the dangerous features of PTP, fish bones and artificial teeth to elderly people and their families, in addition to the danger of coins and beans to the parents of infants.